Question: Which of the following numbers is a multiple of 10? ${55,75,79,80,98}$
The multiples of $10$ are $10$ $20$ $30$ $40$ ..... In general, any number that leaves no remainder when divided by $10$ is considered a multiple of $10$ We can start by dividing each of our answer choices by $10$ $55 \div 10 = 5\text{ R }5$ $75 \div 10 = 7\text{ R }5$ $79 \div 10 = 7\text{ R }9$ $80 \div 10 = 8$ $98 \div 10 = 9\text{ R }8$ The only answer choice that leaves no remainder after the division is $80$ $ 8$ $10$ $80$ We can check our answer by looking at the prime factorization of both numbers. Notice that the prime factors of $10$ are contained within the prime factors of $80$ $80 = 2\times2\times2\times2\times5 10 = 2\times5$ Therefore the only multiple of $10$ out of our choices is $80$. We can say that $80$ is divisible by $10$.